Recently, due to the refinement of semiconductor manufacturing processes, as the gate length of a transistor decreases, the overall chip size and power consumption a semiconductor chip decrease and a speed of operation increases. Although these changes are merits for a digital circuit, this is not the case for an analog circuit, because such changes result in a decrease in the impedance of a power voltage and an output impedance of a transistor. Thus, sensitivity of a circuit to external noise increases, a dynamic range decreases, and a limitation in linearity increases.
Due to the above, available portions of many circuits designed in an analog domain are transferred to a digital domain to overcome such limitations in designing an analog circuit. Also, a great deal of research and development has improved the merits of a digital circuit, for example, insensitivity to noise, reductions in time and costs for design/development, and reductions in size and consumption power.
A low noise amplifier (LNA), a radio frequency (RF) mixer, a phase locked loop (PLL), a channel select filter, an intermediate frequency (IF) mixer, an automatic gain controller, which are included in a super-heterodyne analog receiver that is one sort of an analog RF receiver, are implemented in an analog domain.
As the design process pushes analog devices to become smaller and more refined, the analog receiver consequently has problems, such as an increase in design limitations and a deterioration in the operational characteristics of each block, as described above. To maintain the overall performance of an analog receiver, power consumption is increased or an additional filter or a gain block is necessary. Also, most analog receivers need additional correction circuits to overcome some of these limitations.